Re: Thread milling & DolphinPartmaster CAD/CAM

If anyone wants to play around with thread milling without spending
the money for thread mills, you can make a servicable thread mill via
modifying a tap. Take a standard tap and grind off all but one of the
flutes (actually you're grinding off the part that's NOT a flute :),
and then grind an angled relief behind the remaining cutting edge.
Grind the end of the tap back to where you have fully formed threads,
and you have a poor man's thread mill. I did this a while back to
mill some 1.5"-20 threads in blind holes in aluminum. Used a 1/2-20
tap to make the cutter. Milled about 12 threads like this and the
last one looked as good as the first. If the material had been steel
I might have had to relieve part of the threads and make more than one
turn, but with the aluminum I was able to leave all the threads intact
on the tap and do the entire thread in slightly over one revolution.
Always climb cut to get the best finish. This means you'd drop to the
bottom of the hole and cut a counterclockwise helix moving upward for
a right hand thread.